Spores are a highly resistant, dormant cell type formed by some types of bacteria. Endospores (or simply spores) form within the vegetative mother cell in response to adverse changes in the environment, most commonly nutrient depletion. The mother cell undergoes an asymmetrical cell division, where it replicates its genetic material, which is then surrounded by multiple concentric and spore specific layers. The mother cell then disintegrates, releasing the mature dormant spore which requires neither nutrients, water nor air for survival and is protected against a variety of trauma, including extremes of temperature, radiation, and chemical assault. Spore forming bacteria cause a number of serious diseases in humans, including botulism, gas gangrene, tetanus, and acute food poisoning. Anthrax results from infection by the aerobic spore form Bacillus anthracis. 